Use neutral identifiers in the challenge fixtures

[vvillait88]

Summary

The stripe/charge and solana/charge fixtures in tests/www-authenticate.test.ts were captured from a store that is being shut down. The realm and the store-specific identifiers in the encoded requests (the Stripe network profile and the Solana recipient) are now neutral placeholders. Everything the tests assert is unchanged: amount, currency, decimals and payment method types.

Type of change

• Bug fix (no breaking change)
• New feature (no breaking change)
• Breaking change (existing callers must update)
• Docs, tests, or internal maintenance only

Public API

None.

Test plan

bun run lint exits 0 and bun run test passes (the file's 10 tests, and the full suite). No release: nothing shipped changes.

Checklist

• Tests cover the new behavior, and the suite passes locally
• Lint, format, and type checks pass
• Docs and README examples updated if the public surface changed (no public surface change)
• No secrets, credentials, or personal data in the diff or the tests